Pediatric Cor Triatriatum

Cor triatriatum is a rare congenital cardiac anomaly in which a fibromuscular membrane divides the atrium in two. In its most common form, cor triatriatum sinister, the left atrium is divided into an upper chamber that receives the pulmonary veins and a lower chamber that is related to the left atrial appendage and the mitral valve orifice.[1]

The location of the atrial appendage is a key landmark in this congenital malformation. It differentiates cor triatriatum from a physiologically similar condition, supravalvular mitral stenosis. In cor triatriatum the left atrial appendage is invariably associated with the lower chamber, which is below the membrane.

Rarely, a fibromuscular membrane that is a remnant of the right valve of the sinus venosus divides the right atrium; this finding, so-called cor triatriatum dexter, is usually asymptomatic and is mostly reported as an incidental finding.[2] However, fetal right ventricular hypoplasia has been described associated with this anomaly and has been hypothesized to result from abnormal fetal circulation leading to growth restriction of the fetal right ventricle.[3] Owing to its clinical relevance, the remainder of this chapter focuses on cor triatriatum sinister.

Cor triatriatum represents 0.1% of all congenital cardiac malformations and may be associated with other cardiac defects in as many as 50% of cases. Examples of associated cardiac defects include atrial septal defect, persistent left superior vena cava with an unroofed coronary sinus, partial anomalous pulmonary venous connection, ventricular septal defect, and more complex cardiac lesions, such as tetralogy of Fallot, atrioventricular canal, double outlet right ventricle, and even transposition of the great vessels.[4] Associated bicuspid pulmonary valve, aortic valve atresia, and heterotaxy have also been described.[5]

In classic cor triatriatum, the pulmonary venous chamber receives all pulmonary veins and it drains into the left atrium through a variable-sized orifice. The natural history of this defect depends on the size of the communicating orifice between the upper and lower atrial chambers. If the communicating orifice is small, the patient presents critically ill and may succumb at a young age (usually during infancy) to congestive heart failure and pulmonary edema. If the connection is larger, patients may present in childhood or young adulthood with a clinical picture similar to that of mitral stenosis. Cor triatriatum may also be an incidental finding when it is nonobstructive.

Other anatomical variants of cor triatriatum include a pulmonary venous chamber that receives part of the pulmonary veins and communicates with the left atrium, and a pulmonary venous chamber receiving all or part of the pulmonary veins that does not connect with the left atrium.

Congenital pulmonary vein stenosis is a very rare association with cor triatriatum.[6] Variable types of subtotal cor triatriatum may be noted, with only the right or left pulmonary veins draining into the upper chamber.[7]

Initially, the fetal lungs and pulmonary veins are connected to the systemic venous circulation. Subsequently, a dorsal outgrowth from the common atria, also referred as common pulmonary vein, evaginates and joins the pulmonary veins, whereas the connection to the systemic circulation disappears. As the fetal heart grows, the common pulmonary vein is completely absorbed. Failure of this dorsal outgrowth to join the pulmonary veins results in total anomalous pulmonary venous drainage (TAPVD). An abnormal connection between the common pulmonary vein and the atria results in any of the variants of cor triatriatum.

The critical anatomic feature of cor triatriatum is a diaphragm that divides the left atrium into 2 chambers (see the videos below).

It consists of fibromuscular tissue, and the proximal chamber that is created represents a vestigial common pulmonary vein. The pulmonary veins thus drain into the proximal chamber.

Outcome depends on the size of the communication to the distal chamber, which communicates with the mitral valve. If present, a patent fossa ovalis or secundum atrial septal defect permits decompression of the proximal chamber into the right atrium.

The presentation of cor triatriatum is one of decreased cardiac output and pulmonary venous hypertension. If a connection between the common pulmonary venous chamber and the right atrium is present, pulmonary overcirculation may result in significant right ventricular enlargement.

No known risk factors or associated genetic abnormalities have been reported with cor triatriatum.

Embryologically, the common pulmonary vein is normally absorbed and incorporated into the left atrium. Incomplete absorption results in a fibromuscular membrane that subdivides the left atrium into two chambers resulting in cor triatriatum.

Observation that a left superior vena cava is frequently associated with this lesion has led some to propose impingement of the left superior vena cava to the developing left atrium as a potential pathogenesis.

United States data

Cor triatriatum is a very rare malformation. Incidence is approximately 0.1-0.4% of all infants with congenital cardiac disease.

Race-, sex-, and age-related demographics

No race predilection is reported, but a slight male predilection is observed, with a male-to-female ratio of 1.4:1.

The diagnosis is primarily made in infancy. Later presentation does occur but is usually in childhood or early adulthood; in this patient population, 85% are younger than 40 years. Rarely, patients presenting in their eighth or ninth decade of life have been reported.

Prognosis in symptomatic infants with cor triatriatum without surgical repair is poor with a mortality rate of 75%.

Presence of associated cardiac anomalies adversely affects prognosis.

If the connection between the proximal and distal chambers is not restrictive or if an atrial septal defect is present, prognosis is improved. In this subset of patients, the defect may escape detection in infancy and present later in life.

Mortality associated with surgery is primarily in the immediate postoperative period and patients that survive can expect a late mortality rate of less than 10% and a near normal life expectancy. Late survivors have essentially normal lifestyles without sequelae from the anomaly or surgical correction. The short-term, 30-day mortality rate is 15-20%. Recurrence of cor triatriatum has been described.[6]

Morbidity/mortality

Approximately 75% of patients die in infancy (generally from pulmonary hypertension) if the defect is unrepaired. If the communication between the proximal and distal chambers is not restrictive or if an atrial septal defect allows decompression of the hypertensive left atrium, the prognosis is significantly improved.

The only treatment is surgical correction.[8]  Most postoperative deaths occur in the first 30 days. The early mortality rate in each large series was consistently 15-20%. Early deaths had a higher rate of associated severe cardiac anomalies.

Long-term results are excellent, with long term survival of 80-90% in patients surviving surgery. Survivors have excellent functional results without residual sequelae and a life expectancy that approaches that of the general population. This is particularly true when repair is performed in infancy.

Complications

If the condition is unrecognized and untreated, problems include pulmonary edema, right heart failure, and death. There are case reports of cor triatriatum causing shock infants in infants[9, 10, 11] and pulmonary hypertension in toddlers,[12] particularly in pediatric patients with other congenital heart anomalies.

Late complications include recurrence of the obstructive membrane with recurrence of symptoms.[6]  Similar symptoms may occur later on in life if the membrane is incompletely excised.

Ischemic stroke as a late complication from undiagnosed cor triatriatum (sinister) in an adult has been described.[13, 14]

Cor triatriatum is essentially a form of left atrial inflow obstruction and presents with signs and symptoms of pulmonary venous obstruction.

Most patients present during infancy with a restrictive opening in the membrane. These infants usually present with evidence of low cardiac output, including pallor, diminished peripheral pulses, and tachypnea.

Feeding difficulties, poor weight gain, and respiratory distress are common.

Presentation later in life is less classic; however, when the patient becomes symptomatic, evidence of pulmonary venous obstruction predominates. In these patients, the membrane may become calcified with its orifice becoming smaller or the patient may develop mitral valve insufficiency. These patients may also present with arrhythmias secondary to an enlarged, hypertensive atrium.

Despite the intracardiac defect, no characteristic murmur or pathognomonic physical characteristics are present in patients with cor triatriatum. This often leads to incorrect diagnosis of primary pulmonary vascular or parenchymal disease.

Signs of pulmonary venous obstruction and pulmonary hypertension are present. A right ventricular lift and accentuation of the pulmonary second sound are frequent and may be accompanied by an early diastolic murmur of pulmonary insufficiency. Rales may be present in the lung bases.

A soft, continuous murmur may be present due flow across the membrane. A murmur at the left sternal border is heard in patients with an atrial septal defect and a left-to-right shunt. A diastolic rumble of mitral stenosis at the apex is generally not heard with cor triatriatum.

Low cardiac output manifests as pallor, tachypnea, and diminished peripheral pulses.

Children are typically small, suffering from poor weight gain.

Patients presenting later in life may be dyspneic with a history of frequent pulmonary infections. They may have signs of right-sided heart failure, including distended peripheral veins and hepatomegaly. Signs and symptoms of pulmonary hypertension may be severe.

No specific laboratory studies are indicated in patients with suspected cor triatriatum.

Electrocardiographic (ECG) findings are nonspecific in those with cor triatriatum and may range from normal in asymptomatic older patients to mimicking those findings of a patient with the clinical picture of pulmonary hypertension.

In some patients, ECG may reveal the following:

• Atrial arrhythmias[15]

• Right-axis deviation

• Right atrial enlargement depicted by enlarged P waves

• Right ventricular hypertrophy

Chest radiographic findings are usually nonspecific in cor triatriatum, but they may include pulmonary congestion with diffuse haziness or Kerley B lines and the ground glass pattern of acute pulmonary edema in hilar areas.

Patients may have mild cardiac enlargement and prominence of the pulmonary arterial segment.

The dilated proximal chamber may produce the appearance of left atrial enlargement.

Presence of an atrial septal defect or of an associated partial anomalous pulmonary venous connection adds pulmonary overcirculation to the pulmonary venous obstruction.[16] The radiograph may then reveal significant right ventricular enlargement.

Echocardiography is often sufficient for diagnosis of cor triatriatum, and is the diagnostic modality of choice.[17] See the image below.

The membrane dividing the left atrium can be visualized using 2-dimensional echocardiography, as can the presence of an associated atrial septal defect. The origin of each of the pulmonary veins should be identified to exclude the presence of anomalous pulmonary venous return.

The distinction between cor triatriatum and a supramitral ring should be made by the location of the left-atrial appendage. Differentiating between cor triatriatum and total anomalous pulmonary venous drainage to the coronary sinus may be difficult.

Common cardiac anomalies can also be demonstrated

Transesophageal echocardiography (TEE) and intracardiac echocardiography offer precise image definition and spatial relationship of the membrane.

TEE is very useful in larger and older patients in whom transthoracic images are suboptimal especially in visualizing the left atrium.[18]

Angiography is generally indicated in cor triatriatum to assess pulmonary venous return and pulmonary arterial pressures. Because approximately 10% of patients have partial anomalous venous return, angiography is helpful in defining the precise venous anatomy.

When performed, catheterization generally reveals pulmonary hypertension in a degree that varies directly with the severity of obstruction to pulmonary venous drainage.[15] Demonstration of a pressure gradient between the left atrium and capillary wedge pressure is classic.

The proximal chamber is visualized during the venous phase, and a delay then occurs before the true left atrium and left ventricle are visualized. The proximal chamber then remains opacified and does not contract with the distal chamber.

Both Computed tomography (CT) scanning and magnetic resonance imaging (MRI) provide very detailed anatomic images.[19, 20, 21] MRI has the advantage of not subjecting the patient to radiation.[22, 23]

Cor triatriatum on CT angiography shows a septum dividing the left atrium, with the proximal chamber receiving blood flow from the pulmonary veins.[24]

In classic cor triatriatum, cardiac catheterization reveals pulmonary hypertension without a left-to-right shunt. Pulmonary wedge pressures are high and left atrial pressures are within normal limits. Angiography via pulmonary artery injection shows an opacified pulmonary venous chamber draining into the left atrium.

Histology plays no part in the diagnosis of cor triatriatum; however, pulmonary hypertension results in well-defined structural changes.

There may be pulmonary edema and alveolar hemorrhage with lymphatic dilatation. Increased pulmonary arterial muscularity is present very early, with increased thickness of the arterial wall and extension of muscle into the arterioles. Necrotizing arteriolitis may be present.

The goal of medical care in cor triatriatum is to reduce the symptoms caused by pulmonary venous congestion until definitive surgical therapy can be performed.

Patients presenting in extremis should be operated on immediately after resuscitation, without time spent for prolonged medical therapy.

On occasion, extracorporeal membrane oxygenation is initiated to stabilize a patient.

Consultations

Obtain consultations with a pediatric cardiologist and a pediatric cardiac surgeon.

Transfer

Admit patients with cor triatriatum who have undergone surgical treatment to a pediatric ICU experienced in dealing with congenital cardiac defects.

Provide postoperative treatment of heart failure and pulmonary hypertension until pulmonary vascular resistance normalizes.

Diet and activity

No specific dietary restrictions are recommended.

Physical activity should not be limited in patients with early and complete correction.

Patients with persistent pulmonary or cardiac dysfunction secondary to long-standing disease may have moderate restriction of exercise tolerance.

Surgery is the treatment of choice for cor triatriatum. In relatively recent years, interventional catheterization techniques have evolved and been used successfully in some patients.[25]

Surgical correction

Open correction is currently preferred over closed (percutaneous) procedures.

The procedure is performed on cardiopulmonary bypass through an atrial incision with complete resection of the diaphragm.

Interventional cardiology

The role of percutaneous balloon dilation in managing this condition remains to be determined.

Postoperative care

Admit patients with cor triatriatum who have undergone surgical treatment to a pediatric ICU experienced in dealing with congenital cardiac defects.

Provide postoperative treatment of heart failure and pulmonary hypertension until pulmonary vascular resistance normalizes.

Successful surgical correction of cor triatriatum allows a return to a normal lifestyle without restriction of activity or need for medications.

Serial echocardiography is a reliable and effective method for following patients on an outpatient basis. Late complications are rare.

Recurrent membrane stenosis from incomplete surgical resection can occur and is well demonstrated by echocardiography. This imaging modality may also demonstrate residual pulmonary vein stenosis.

Postoperative function and exercise tolerance should approach normal. Long-term activity restrictions are usually unnecessary.

Medical management in cor triatriatum is targeted toward associated elevation in pulmonary vascular resistance and heart failure. It is continued in the postoperative period until the pulmonary resistance falls and right ventricular performance improves. Mainstays of treatment are inotropic agents and diuretics.

Inotropes are used in patients with low cardiac output secondary to heart failure. Agents such as dopamine predominate in the intensive are unit (ICU), whereas agents such as digoxin are sometimes used in the outpatient setting.

Diuretics are used in patients with pulmonary edema.

Patients with pulmonary edema are unlikely to respond to inhaled nitric oxide preoperatively because the pulmonary hypertension is secondary to mechanical obstruction.

Class Summary

Cardiac glycosides (eg, digoxin) increases myocardial contractility in patients with heart failure. Adrenergic and dopaminergic agents (eg, dopamine) provide myocardial support in the perioperative period for patients with heart failure. The more restrictive the connection between proximal and distal chambers, the more likely inotropic support is required. Numerous agents are available in this category.

Digoxin (Lanoxin)

Exerts its inotropic action by increasing the amount of intracellular calcium available during excitation-contraction coupling. It is one of numerous inotropic agents that can be used in infants with congenital cardiac defects. Other agents, such as dopamine (described below), are more appropriate for acute management of heart failure in ICU setting.

Dopamine (Intropin)

Adrenergic agonists are often used in the critical care setting for their rapid onset of action and rapid peak effect. They are, therefore, much easier to titrate to effect in acute settings. Their half-life is also much shorter than digoxin's, and their effects are rapidly lost when drug is discontinued.

Class Summary

These agents are used for management of right heart failure and pulmonary edema.

Furosemide (Lasix)

First-line drug for diuresis in newborns and infants and can be expected to be highly effective. It is a sulfonamide derivative that exerts its effects on the loop of Henle and distal renal tubule, thus inhibiting reabsorption of sodium and chloride.